The present invention is directed to a fastening element to be driven into hard receiving materials, such as metal, and includes a head at its trailing end with means for entraining the head in a driving member for rotating the fastening element, and with a shank extending axially from the head. A cup-like shaped guide member is in threaded engagement with the shank. The shank has a tip at its leading end. The shank has an axially extending thread reaching from the trailing end toward the leading end.
In the past the so-called direct assembly or installation of plate-like members, such as sheet metal plates to a base structure, such as a steel girder, has been known where a nail-like fastening member is driven through the metal plate into the base structure, usually by means of an explosive powder charge. Such a process is effective and results in a high quality attachment, since a cold welding of the fastening element to the base structure takes place. Driving of the fastening element by means of a powder charge is independent of any other power supply, such as compressed air or electrical power. Such attachments can be disassembled, however, only with the destruction of the metal plates.
In another known type of fastening of metal plates, screws have been used. Recently, basically self-tapping screws with a drilling cutting edge have been used, so that the cutting edge drills holes into the metal plate, as well as into the base structure in which a thread is cut. While such an attachment is detachable, the drilling and thread-cutting procedures involve a considerable expenditure of time and the driving step is dependent on the supply source for operating a drilling and/or threading apparatus.
A fastening method for use in the above type of fastening elements is disclosed in DE-OS 24 21 917 which uses the known steps of direct installation by driving a fastening element through the metal plate and then into the base structure. The effective anchoring of the fastening element takes place manually, by means of conventional tooling, such as wrenches and the like. The fastener element used in this fastening method includes a head with means for rotational entrainment, and a threaded shank with a guide disk.
While this known fastening method has the advantage of being independent of any power supply as is the case in direct installation, there is, however, the considerable disadvantage of a high expenditure of time and considerable handling operations, since two procedures follow one after the other consecutively and must be performed with required tools. In other words, the driving-in operation is effected by a setting apparatus powered by an explosive powder charge and then the attachment procedure is completed by means of tools for applying torque to the fastening element.
In DE-OS 35 18 517, a driving device, constructed similar to a explosive powder operated setting device, is capable of performing an axial driving movement and, after completing a specific axial travel, of performing at least a rotational driving movement. The rotational driving movement may possibly overlap with an additional axial travel. The driving device has a twin piston formed by a shaft piston and an annular piston. The driving device operates, at the commencement of the driving procedure, so that the two pistons are accelerated together and when the shaft piston is braked, the annular piston imparts rotational movement to the shaft piston. As a result, it is possible to set thread cutting screws with this known driving device by driving the screws initially axially through metal plates into the base structure and then to brake the shaft piston depending on the resistance to the driving process, whereby with a rotationally locked connection between the shaft piston and the fastening elements, the fastening elements receive rotational movement for the final threading-in operation.
One problem in driving fastening elements with such a known driving device is that, depending upon the resistance to the driving of the fastening element by the metal plate and the base structure, braking of the shaft piston does not always occur at the same rate. If the shaft is prematurely braked, the fastening element is not sufficiently threaded into the base structure, or if there is little resistance to the driving procedure, the braking of the shaft piston occurs at a late point in the driving operation whereby the relatively high energy of the driving device does not afford sufficient threading-in of the fastening member.